An enlarged heart may have several causes. But it's usually the result of high blood pressure or coronary artery disease. It may not pump blood effectively, which can bring congestive heart failure. It may improve over time. But most people with an enlarged heart need life-long treatment with medications.
The heart enlarges because of damage to the heart muscle. Up to a point, an enlarged heart can still pump blood normally. As the condition progresses, though, the heart's pumping ability declines.
Dilated cardiomyopathy is the main type of enlarged heart. The walls of both sides (also known as ventricles) become thin and stretched. This enlarges your heart.
In the other types, the muscular left ventricle becomes very thick. High blood pressure may cause your left ventricle to enlarge (a type known as hypertrophy). The thickening (which doctors call hypertrophic cardiomyopathy) can also be inherited. An enlarged heart keeps more of its pumping ability when it's "thick" rather than "thin."